A computer network is a collection of a number of computers which communicate via a network interface. Typically, this network interface employs a layered communication protocol such as the Transport Control Protocol/Internet Protocol (TCP/IP) or other such communication protocols. Computers then communicate using the communication protocol by sending messages to other computers in the network. Often, these messages are in the form of "packets" of data which typically include a destination address of the computer to receive the data contained in the packet. Layered protocols also often allow for multiple destinations to be specified for a message. Multiple destination messages include broadcast messages (messages which are sent to every computer in the network and/or attached networks) and multi-cast messages (messages which are sent to a specified subset of computers in the network or attached networks).
One difficulty which may arise when multiple destination messages are utilized by a network communications protocol are what is referred to as "broadcast storms." Broadcast storms occur when multiple broadcast or multi-cast messages are generated at approximately the same time. This sudden increase in communications traffic to all or a substantially all of the nodes in the network or networks can result in congestion problems such as buffer overrun in switches, routers or other network interconnection devices.
Previous attempts to reduce broadcast storms include those described in the O'Connell et al. PCT Application WO96/38956. In O'Connell et al., a management entity monitors traffic through all ports of a switch or bridge and compiles statistics on the number of occasions multicast/broadcast data is being supplied. From either the total or supplied data or both the management entity makes a decision as to whether to permit a further multicast/broadcast message to pass through the switch or bridge. If further multicast/broadcast messages are not to pass through the switch or bridge the messages are routed to a non-existent port.
While the O'Connell et al. system may prevent broadcast storms by determining the total broadcast/messages through a switch, the system also prevents what may be essential messages from being transmitted through the switch. Thus, for example, a critical broadcast message may be routed to the non-existent port simply because it came after a large number of non-critical messages. Furthermore, the O'Connell et al. system does not reduce the network traffic associated with broadcast/multicast messages on the networks where the messages originate but simply prevents propagation of the messages to other networks through the switch or bridge.
Additional mechanisms which relate to congestion problems in various communications systems are illustrated in U.S. Pat. No. 5,636,345, U.S. Pat. No. 5,604,867, U.S. Pat. No. 5,463,620, U.S. Pat. No. 5,282,203, and U.S. Pat. No. 5,530,695. In addition, an existing IBM product, the IBM 8271 Ethernet LAN Switch, contains a broadcast suppression scheme that indiscriminately discards all broadcast packets when a user defined threshold is exceeded. These mechanisms, however, generally have some or all of the same limitations as the O.degree. Connell system.
In light of the above discussion, a need exists for improvements in the prevention or suppression of broadcast traffic in computer networks.